2004 Fiscal Year Final Research Report Summary
The preparation of low-resistive p-ZnSe by closed Bridgman method
| Project/Area Number |
14550286
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
WANG J.F. TOHOKU UNIVERSITY, INSTITUTE OF MULTIDISCIPLINARY RESEARCH FOR ADVANCED MATERIALS, Research Associate, 多元物質科学研究所, 助手 (30271977)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Bridgman method / p-ZnSe / carrier concentration / intrinsic defect / annealing / Ohmic contact |
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| Research Abstract |
ZnSe is a promising material for preparing blue light emitting diodes due to its suitable direct band gap of 2.7 eV at room temperature. Recently, there is an urgent demand for large area and high quality ZnSe substrates for homoepitaxial growth. In order to satisfy above requirement, we adopted a closed double-crucible assembly consisting of an inner pBN crucible and an outer molybdenum capsule. As an optimum growth condition, the superheating temperature of 76 ℃, the temperature gradient at the growth interface of 30 ℃/cm and growth rate of 3.6 mm/h have been determined.
Using above growth conditions, the twin-free greenish yellow ZnSe single crystals of cylindrical shape with diameter of 12 mm and length of 55 mm have been obtained by the polycrystalline seeded vertical Bridgman method. Chemical etching on the cleaved (110) plane showed that the average value of etch pit density (EPD) is about 2.0×10^5 cm^<-2>. The rocking curves of 4-crystal X-ray diffraction showed the 19 arcsec in full-width at half-maximum (FWHM). The photoluminescence (PL) spectra at 4.2 K showed the resolved intensive bound exciton emission lines and the very weak donor-acceptor pair (DAP) emission bands and their phonon replicas. Above all results suggest that the ZnSe single crystals grown by the present method is of very high quality.
Furthermore, the low resistivity p-type ZnSe single crystals have been grown by changing the compositions and doping Sb or Bi into starting materials. PL spectra show the typical emission of ZnSe single crystals with high-resistivity, low resistivity p-type. C-V characteristics showed that the highest carrier concentration in p-type ZnSe is 5.5×10^<16> cm^<-3>.
By the way, we also tried to prepare the Ohmic electrodes by using Pd metal. The experimental results showed that Pd is a good candidate for the electrode material of p-ZnSe.
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Research Products
(7 results)
